By James Abbott
I recently attended an industry evening held by WYSIWYG 3D. That’s right, What You See Is What You Get.
3D scanning is the way of the future. This technology uses a combination of laser and camera technology to inspect product. Such machines allow for the timely and accurate monitoring of quality and for easier reverse engineering of products. A by-product of 3D scanning is the ability to store items as images rather than physical entities.
As you well know, inspection of product can be a vital process in manufacturing. In some production runs every part must be measured and a reported on.
This is often the case for the mining industry where every part has a serial number as a reference in the case of failure.
This requirement represents a lot of time and money.
Historically, inspection has been time consuming and a specialised skill. Inspectors traditionally inspected a batch of product already produced, and, if out of tolerance, rejected.
What a waste. Why not inspect product and report on non-conformance during production?
This certainly conforms with Lean Thinking and Six Sigma i.e. define, measure, analyse, improve and control production.
A 3D scan of an item is not only quick, but a highly accurate and efficient method of capturing a digital model of a component.
For example to prove a point, the front façade of Customs House, Sydney, could be scanned in as little as 6 hours. The accuracy would be very high, given that the scan would take a point every 1.2mm.
Having used such a grand example, the accuracy does depend on the application. For example, to scan the front of a building to determine the contours for a lighting display, a high degree of accuracy would not be required, but even so, a low degree of accuracy would be in the range of a measured point every 1.2mm.
Wear and tear can be accurately assessed using 3D scanning. In the mining sector where the buckets used on the heavy loaders can weigh up to 500 tonne and cost as much as $1million, wear is a big consideration.
By scanning at regular intervals, wear can be determined and the bucket replaced when
required, which occurs every three months on average.
Such technology also allows for improved reverse engineering.
The process is as follows:
Essentially, a 3D model is scanned using a 3D scanner to generate a captive CAD model.
The camera then relays an image of the curvature generated by the laser on the article
and converts this image into a model.
It consists of a generated point cloud, which is converted into an IGES model and joined by triangles. All very technical, but the end result is a scanned 3D model of your product to a very high degree of accuracy.
In the world of manufacturing, a high degree of accuracy would be required to repair tooling for example, which could be in the range of a measured point every 0.1mm. Alternatively, smaller components coming off the production line could be individually measured.
In this case, a 3D model would be produced, which could be laid over the CAD model and variations between the two, analysed to identify variation and deviation.
In addition to this, a visual representation could be generated, which means the operator could see instantaneously any problem areas.
A report could be generated and exported to a third party spreadsheet.
This could then be referenced back to a serial number on the component. All with an
accuracy as good as 0.05 micron. Duds can then be easily identified and the process refined with minimal wastage or rework.
Alternatively, components can be reverse engineered using a more manual digitising
Using a laser head with probe, an operator can touch points of an object, which are recorded to make up a 3D model. An operator can take measurements around an object, similar to a Co-ordinate Measuring Machines (CMM), except that the operator has total control.
In particular, the very difficult measurement of holes and tapers can be determined quickly and efficiently. Using this method, an accuracy of 30 micron can be achieved.
Tapered holes in particular have always been difficult to measure.
Simply taking about nine co-ordinates and selecting the “fit cone” option, a cone can be generated and inserted into the model.
This can be converted back to geometry to determine diameter and centre lines.
A by-product of 3D scanning technology is the ability to store items as images.
For example, dental moulds have always presented a problem with archiving.
For legal reasons, most dentists need to provide a facility to store patient dental moulds for 7 years after a patient turns 18.
Now such moulds can be stored electronically and can be 3D printed for as little as $600.
* James Abbott is the Managing Director of Challenge Engineering, specialising in CNC machining and based at South Granville, Western Sydney
Ph: 02 9632 0010